The present invention relates to color change systems for spray coating apparatus, and in particular to improved color change systems for rapidly changing from spraying coating material of one color to spraying material of another color.
Color change systems for spray coating apparatus have particular application in industrial operations where articles or ware are to be spray coated at a spray station, or are to be coated as they move along a production line. Where the articles are required to be coated a wide variety of colors, it is generally not practical to establish separate spray stations or production lines for each color, or even to spray a long sequence of articles of one color, then another long sequence of articles of a second color, etc. Instead, it is desirable to be able to make color changes rapidly and simply at a single spray station.
Color change systems are useful in such cases, and provide for a variety of colors to be sprayed from a single spray gun. With many conventional systems, a plurality of supply containers of fluid, each of a different color and having a separate motor driven fluid pump, are connected with a manifold through valve controlled ports. An outlet from the manifold connects with an inlet to the spray gun, and to spray material of a particular color the port valve associated therewith is opened and the motor driven pump for the supply is energized to provide the fluid through the manifold to the gun. After completion of spraying coating material of a particular color, the manifold and gun are flushed with solvent and compressed air to clean the system in preparation for spraying material of a different color.
Although the foregoing types of color change systems provide versatility in spraying a plurality of different colored fluids with a single spray gun, they suffer the disadvantage of requiring a separate motor driven pump for each supply container of fluid, and are therefore expensive because of the large numbers of pumps involved. For limited use on small production lines, their costs often cannot be justified. In addition, requisite manifold flushing between color changes imposes time limitations on the color change process, which limitations may become significant in use of high solids paints which do not flush rapidly. Consequently, such systems also lack versatility for use with production lines in which rapid color changes are necessary.
One prior effort to minimize the costs of color change systems of the aforementioned type contemplates use of a single motor driven pump at the outlet from the manifold, instead of separate motor driven pumps for each supply container of fluid. In this case, lines extend between the valve controlled ports of the manifold and the supply containers, whereby fluid of a selected color may be connected through the manifold with the pump for delivery to the spray gun. Although use of a single motor driven pump signficantly decreases system cost, the pump along with the manifold must be cleansed between color changes, so that this type of system also suffers from significant time delays between color changes, particularly in use of high solids paints, which are increasingly being turned to because of decreased environmental pollution incident to their use.